[xj-s] ecu - fault?

i have hot idle - 1100rpm
after disconection of ECU vacum pipe , idle goes to 500 .
is that proper?

what does that mean about?
still leaks? or ecu problem??

i described that in (’‘two in one - continuation’’ - down the topic
list, but I dont know if thats going to be there still tomorrow)

thnks in advance

adam–
adam XJ-S 5,3HE '84 coupe
cracow, Poland
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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In reply to a message from atyp1 sent Mon 14 Apr 2003:

no ideas, I can see:-)
so maybe someone knows, …what is happening with fuel mixture, when
engine is working on idle, …and you disconnect ECU and close the
pipes?
is that going lean? or rich?
and what should be the proper idle rpm than?

thanks in advance in some friendly advice

greatings for all

adam–
adam XJ-S 5,3HE '84 coupe
cracow, Poland
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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At 23:50 2003-04-14 +0200, atyp1 did say:

i have hot idle - 1100rpm
after disconection of ECU vacum pipe , idle goes to 500 .
is that proper?

what does that mean about?
still leaks? or ecu problem??

Well, lessee, if you disconnect the vacuum line from the ECU, the ECU won’t
have accurate information about the engine, so the fact that something
changes should be good sign for you. Also, unless that line is plugged,
you’ve introduced a vacuum leak to the engine.

Is there a specific reason you suspsect the ECU of being the source of your
problem? The ECU controls fuelling, but in and of itself cannot change
your RPM - that’s an airflow issue.

I don’t recall that you’ve yet ruled out the SAV (at the front of the A
bank air cleaner housing) or indicated what happens when you simply block
off the AAV intake line (at the rear of the B bank air cleaner housing).

Until you rule out the obvious sources of extra airflow, the rest of the
diagnostics really amount to a waste of time.

i described that in (’‘two in one - continuation’’ - down the topic
list, but I dont know if thats going to be there still tomorrow)

The messages don’t dissappear - they remain forever in the archives, and
the people to which they were delivered to via email may or may not choose
to retain them. If someone elected to purge a message from their own
inbox, that would be their prerogative - resending it won’t make them any
more likely to read it.

Hopscotching the subject line as well as the list won’t help the diagnostic
process along any faster either, since previous diagnostic discussion now
sits under two other topics, including one in another forum, which
complicates the process of checking to see what has already been suggested
and what you’ve already checked.

My suggestion: check your SAV and AAV air sources. And of course, the
obvious: checking the throttle plate adjustments and the AAV adjustment.

http://jaguar.professional.org/
Sean Straw '88 Jaguar XJ-SC 5.3L V12 (LHD) ‘Black Cat’ 65K
Marin County, California '85 Jaguar XJ-S 5.3L V12 (LHD) ‘Bad Kitty’ 210K
'69 Buick GranSport 455 V8 324K

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